Surgical tables

ABSTRACT

A surgical table having a tabletop and a column for enabling at least a part of the tabletop to be rotatable about a trend axis extending in a transverse direction across the tabletop; and an actuator mechanism coupled between the movable framework and the column and arranged to raise and lower the movable framework and the trend axis relative to the column and to rotate the movable framework about the trend axis, wherein the actuator mechanism is fitted to an external surface of the outer column element and is adapted to move the movable framework between a lowermost position, at which the trend axis extends through an upper part of the outer column element which surrounds the inner column element when the column elements are telescoped into the contracted configuration, and an uppermost position, at which the trend axis is spaced at spacing height from an uppermost part of the column.

FIELD OF THE INVENTION

The present invention relates to surgical tables.

BACKGROUND

Surgical tables, or operating tables, comprising a base for standing ona floor, a column extending from the base, and a tabletop providing apatient support surface are well known. There is a general need in theart for surgical tables to have variable height to enable the tabletopto be located at a selected height which is most suitable for therequired surgical, therapeutic or diagnostic treatment of a patientpositioned on the surgical table. The column is extendable, typically bya telescoping arrangement, to allow the column to be moved betweencontracted and extended positions in order to lower and/or raise thetabletop to a desired height.

SUMMARY OF THE INVENTION

There is a particular need in the art for the column to have a widerange of lengths to enable the tabletop to be located at any positionwithin a wide range of heights. The column has a most contractedconfiguration and a most extended configuration, and the distanceseparating those configurations constitutes the operating range of thecolumn. The column is adapted to be movable to any position within thatoperating range.

It is particularly desired for the column to be structured so that whenthe column is in the most contracted configuration, at which thetabletop is at the lowest position of the height range, the height ofthe tabletop above the floor on which the surgical table is standing isas low as possible. A low operating height for the surgical table canprovide easier loading and unloading of the patient onto and from thesurgical table. Also, a low operating height for the surgical table canmore easily permit laproscopic surgery and improves the ergonomics ofthe table for the surgeon.

However, it is also particularly desired for the column to be structuredso that when the column is in the most extended configuration, at whichthe tabletop is at the highest position of the height range, the heightof the tabletop above the floor on which the surgical table is standingis as high as possible. A high operating height for the surgical tablemay be required for some operating procedures, for example orthopaedicsurgery.

Therefore there is a need for a wide operating range for the tabletopheight and also the ability to provide as low a height as possible forthe lowest position of the tabletop within that operating range.

Still further, the tabletop of the surgical table is generally requiredto be movable relative to the column so as to be tiltable about twoorthogonal horizontal axes, namely a tilt axis extending longitudinallyalong the length of the tabletop and a trend axis extending transverselyacross the length of the tabletop.

The structure of the tabletop and the column, and of the actuatormechanisms to move the tabletop relative to the column about the tiltaxis and/or the trend axis, must enable free movement about the tiltaxis and/or the trend axis over a wide range of tilt/trend angles, andover a wide range of table operating heights.

Therefore there is a need for a wide operating range for the tabletopheight and also the ability to provide as low a height as possible forthe lowest position of the tabletop within that operating range whilestill permitting wide tilt/trend functionality.

In addition, there is a generally need for the column and the associatedactuator mechanisms which raise and lower the tabletop to have a smallcross-sectional area, with small length (in the table length direction)and width (in the table width direction), so that the “footprint” of thecolumn in minimised. This in turn can permit the dimensions of the baseto be minimised, which assists access to the patient by medicalpersonnel.

Finally, the weight of patients is generally increasing as a result ofincreasing obesity in some countries. The column must be capable ofbearing a vertical load of, for example, more than 500 kg and must becapable of bearing a correspondingly high offset load, when the tabletopis tilted about the trend or tilt axis.

Current commercial surgical operating tables have a typical minimumoperating height of 580 to 600 mm or higher. In this specification the“minimum operating height” of an operating table means the minimumheight of all parts of the entire tabletop surface, including the partof the tabletop that is located directly above the column, relative tothe floor when the operating table is free-standing on the floor. Themeasurement is made without any mattresses which are conventionallyremovably placed onto the tabletop. The operating table may have a basewhich is movable, for example incorporating castors, or fixed, forexample having fixed feet.

The requirement that the height must be measured for all parts of theentire tabletop surface means, for example, that the minimum heightcannot be measured simply by measuring the height of a head portion ofthe tabletop when the head portion is lowered into a trendconfiguration, and so the head portion is a lowermost part of thetabletop and the centre and leg parts of the tabletop are significantlyhigher, with the leg portion being higher than the part of the tabletopthat is located directly above the column.

There is a need in the art to provide a surgical table which has a lowerminimum operating height, but which can also have a wide range of heightadjustment, high trend and reverse trend angles and a small columnfootprint.

There is a need for a surgical table with a more compact mechanism fordisposing a tabletop in a wide range of different configurations.

The present invention provides a surgical table.

Optional and/or preferred features are defined in the variousembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described byway of example only with reference to the accompanying drawings, inwhich:—

FIG. 1 is a schematic side view of a surgical table in accordance withan embodiment of the present invention;

FIGS. 2 a and 2 b are each is a schematic perspective side view fromabove of the column and a mechanism for controlling the trend angle andheight of a trend frame of the surgical table of FIG. 1 , respectivelyshowing the column at minimum height and the trend frame at minimumheight and the column at minimum height and the trend frame at maximumheight;

FIG. 3 is a schematic side view of the column and the mechanism forcontrolling the trend angle and height of the trend frame of thesurgical table of FIG. 1 , showing the column at minimum height and thetrend frame at minimum height;

FIG. 4 is a schematic side view of the column and the mechanism forcontrolling the trend angle and height of the trend frame of thesurgical table of FIG. 1 , showing the column at minimum height and thetrend frame at maximum height;

FIG. 5 is a schematic side view of the column and the mechanism forcontrolling the trend angle and height of the trend frame of thesurgical table of FIG. 1 , showing the column at minimum height and thetrend frame at an intermediate height, and with the trend frame at areverse trend angle of 45°;

FIG. 6 is a schematic side view of the column and the mechanism forcontrolling the trend angle and height of the trend frame of thesurgical table of FIG. 1 , showing the column at FIGS. 7 a, 7 b and 7 care schematic side views of the column and the mechanism for controllingthe trend angle and height of the trend frame of the surgical table ofFIG. 1 , showing the trend axis at an intermediate height and the trendframe respectively in a horizontal configuration, in a reverse trendconfiguration and in a trend configuration;

FIGS. 8 a, 8 b and 8 c are schematic side views of the column and themechanism for controlling the trend angle and height of the trend frameof the surgical table of FIG. 1 , showing the trend axis at a minimumheight and the trend frame respectively in a horizontal configuration,in a reverse trend configuration and in a trend configuration;

FIG. 9 is a schematic side view of the column and the mechanism forcontrolling the trend angle and height of the trend frame of thesurgical table of FIG. 1 , showing the column at an intermediate heightand the trend frame in a reverse trend configuration;

FIG. 10 is a schematic perspective side view of an embodiment of astabiliser for the mechanism for controlling the trend angle and heightof the trend frame of the surgical table of FIG. 1 ;

FIG. 11 is a schematic cross-section through the stabiliser of FIG. 10 ;

FIG. 12 is a schematic plan view of the column and the mechanism forcontrolling the trend angle and height of the trend frame of thesurgical table of FIG. 1 ;

FIG. 13 is a schematic bottom view from below of the column of thesurgical table of FIG. 1 ;

FIGS. 14 a and 14 b are each a schematic perspective view of a lockingand/or braking mechanism of the surgical table of FIG. 1 at respectivedifferent heights of the movable framework relative to the column;

FIG. 15 illustrates a cable management system for the column of thesurgical table of FIG. 1 , with the column in a contractedconfiguration;

FIG. 16 illustrates the cable management system of FIG. 15 , with thecolumn in an extended configuration;

FIGS. 17 a and 17 b schematically illustrate the cable configuration inthe cable management system of FIG. 15 when the column is in thecontracted or extended configuration respectively;

FIG. 18 is a schematic perspective side view from above of a column anda mechanism for controlling the trend angle and height of a trend frameof a surgical table in accordance with a further embodiment of thepresent invention;

FIG. 19 is a schematic perspective view of a tilt mechanism of asurgical table in accordance with an embodiment of the presentinvention;

FIGS. 20 a and 20 b illustrate a tilt frame of the tilt mechanism ofFIG. 19 rotated about the tilt axis at two opposite end positionsrelative to a central level position;

FIG. 21 is a schematic perspective view of a tilt mechanism of asurgical table in accordance with a further embodiment of the presentinvention;

FIG. 22 is a schematic perspective view of a tilt mechanism of asurgical table in accordance with a further embodiment of the presentinvention;

FIG. 23 is a schematic perspective view from one end view of a tiltmechanism of a surgical table in accordance with a further embodiment ofthe present invention with the tilt frame in a level configuration;

FIG. 24 is a schematic perspective view from the opposite end of the atilt mechanism of FIG. 23 with the tilt frame in a level configuration;and

FIG. 25 is a schematic side view of the tilt mechanism of FIG. 23 withthe tilt frame in an inclined configuration.

DETAILED DESCRIPTION

Referring to FIGS. 1 to 17 b, a surgical table, designated generally as2, comprises a base 4 or standing on a floor. The base 4 typicallyincludes wheels for moving the table 2 along the floor. Alternatively,the base 4 may be fixed, for example having fixed feet. A column 6 ofadjustable height is mounted on and extends from the base 4. A tabletop8, which provides a patient support surface 10, is supported above thecolumn 6.

As described hereinafter, the surgical table 2 includes a mechanism forinclining the tabletop 8 relative to the column 6 by inclining thetabletop 8 about transverse and longitudinal horizontal axes of thetabletop 8. Inclination about the transverse horizontal axis of thetabletop 8 is referred to in the art as “trending”, while inclinationabout the longitudinal horizontal axis of the tabletop 8 is referred toas “tilting”. Compound movements also are possible, in which thetabletop 8 is inclined about both the transverse and longitudinal axesof the tabletop 8 at the same time.

As used herein, the longitudinal axis of the tabletop 8 is the majoraxis of the tabletop 8 and the transverse axis of the tabletop 8 is theorthogonal minor axis of the tabletop 8. The longitudinal direction ofthe tabletop 8 is parallel to the major axis and the transversedirection of the tabletop 8 is parallel to the minor axis. That is, thetransverse direction of the tabletop 8 is perpendicular to, ororthogonal to, the longitudinal direction of tabletop 8.

As depicted in FIG. 1 , the tabletop 8 is typically divided into fivesections, namely a head section 12, an upper torso section 14, a lowertorso section 16 and a pair of laterally adjacent leg sections 18, ofwhich only one is shown in FIG. 1 . The lower torso section 16 iscoupled to the column 8. Each of the sections of the tabletop 8 providesa portion of the patient support surface 10, and each of the sectionshas a respective separate mattress (not illustrated) removably fitted tothe respective section. As is well known in the art, the tabletopsections can be individually moved relative to an adjacent section andsome sections can be detached from the tabletop 8.

Referring in particular to FIGS. 6, 12 and 13 , the column 6 comprises aplurality of column elements 30, 32, 34 which form a telescopingassembly 36. The telescoping assembly 36 surrounds an actuator 37, whichis shown schematically and in phantom in FIG. 13 , for raising andlowering the column 6. The actuator 37 comprises a column drivemechanism located within the inner column element 34 of the plurality ofcolumn elements 30, 32, 34. The plurality of column elements comprisesan outer column element 30 and an inner column element 34. The outercolumn element 30 externally surrounds the inner column element 34 anddefines an external surface 38 of the column 6 when the column elements30, 32, 34 are telescoped into a contracted configuration. The pluralityof column elements further comprises at least one intermediate columnelement 32 between the outer column element 30 and the inner columnelement 34. In the illustrated embodiment there is only one intermediatecolumn element 32, although a telescoping series of plural intermediatecolumn elements 32 may be provided.

The actuator 37 typically comprises an electric actuator 37. Theactuator 37 is coupled between the outer column element 30 and the base4 and drives the outer column element 30 upwardly and downwardlyrelative to the base 4, with the plurality of column elements 30, 32, 34being coupled together so as to be raised or lowered in synchronism. Theactuator 37 has an upper end 39 coupled to a drive surface 41 affixed tothe outer column element 30 of the plurality of column elements, and thedrive surface 41 is a provided by a plate 43 located inwardly of, andaffixed to, the outer column element 30.

The actuator 37 may comprise a two-stage synchronised telescopicleadscrew, or ballscrew/leadscrew combination. The lifting load isdirected entirely through the leadscrew ballscrew/leadscrew combinationand there are no axial bearings required to support the lifting load.Alternatively, the actuator 37 may comprise two ballscrews, or aleadscrew/ballscrew combination. In this specification a ballscrewcomprises a type of leadscrew and so when a reference is made herein toa leadscrew that term may also be construed to encompass a ballscrew.

Position sensors and high/low limit switches may be provided on thecolumn 6. End stops may be provided to limit the high/low positions ofthe plurality of column elements.

The column 6 comprises a plurality of linear motion guide units 40between each pair of adjacent column elements 30, 32, 34. The linearmotion guide units 40 are recirculating ball-type linear guides. Thelinear motion guide units 40 extend in a telescoping direction D and aremutually spaced. There is a pair of linear motion guide units 40 betweeneach pair of adjacent column elements 30, 32, 34. The linear motionguide units 40 of each pair are located on opposite sides of the trendaxis T-T and on opposite sides of a tilt axis X-X orthogonal to thetrend axis T-T.

The column 6 has a substantially rectangular cross-section, which in theillustrated embodiment is a square cross-section, for example havingdimensions of 180 mm×180 mm. Each pair of linear motion guide units 40are located at opposite corners 42 of the rectangular cross-section.

The column elements 30, 32, 34 are thin-walled tubular sections. Thelinear motion guide units 40 located at opposite corners 42 a, 42 b, 42c, 42 d of the rectangular cross-section maximise the torsional rigidityof the column structure and equalise the offset load capability in boththe cranial and caudal directions. The maximum footprint of the column 6is typically 180 mm×180 mm.

As shown in the illustrated embodiment, the column 6 has oneintermediate column element 32 between the outer column element 30 andthe inner column element 34. A first pair of linear motion guide units40 a, 40 b between the outer column element 30 and the intermediatecolumn element 32 are located at first opposite corners 42 a, 42 b ofthe rectangular cross-section and a second pair of linear motion guideunits 40 c, 40 d between the inner column element 34 and theintermediate column element 32 are located at second opposite corners 42c, 42 d of the rectangular cross-section.

Each linear motion guide unit 40 comprises an elongate channel 44 fixedto one column element of the pair of adjacent column elements and anelongate bar 46 fixed to the other column element of the pair ofadjacent column elements, the elongate bar 46 being slidable in theelongate channel 44. Bearings, not shown, are provided between theelongate bar 46 and the elongate channel 44 to provide a low frictionslider arrangement. Preferably, the elongate channel 44 is fixed to anouter column element of the pair of adjacent column elements and theelongate bar 46 is fixed to the inner column element of the pair ofadjacent column elements.

As shown particularly in FIGS. 2 a to 13, the surgical table 2incorporates a mechanism for controlling the trend angle and height of atrend frame 50, which is beneath the tabletop 8. The trend frame 50 canbe rotated about a trend axis, and the angle of inclination of the trendframe 50 sets the trend angle of the tabletop 8.

Referring in particular to FIGS. 2 a to 8 c , a movable framework 50,constituting a trend frame 50, is mounted between the tabletop 8 and thecolumn 6. The movable framework 50 enables at least a part of thetabletop 8, for example the lower torso section 16, to be rotatableabout the trend axis T-T. The trend axis T-T extends through the movableframework 50 in a transverse direction across the tabletop 8. The tiltaxis X-X extends through the movable framework 50 and is orthogonal tothe trend axis T-T. The tilt axis X-X is parallel to a centrallongitudinal axis C-C of the tabletop 8.

The trend frame 50, provided by the movable framework 50, is adapted tomove about the trend axis T-T, and a tilt frame (not shown) is mountedabove the movable framework 50 at the pivot points 500 shown in FIG. 2 ato enable the tilt frame to move independently by a separate drivesystem (not shown) about the tilt axis X-X. Various drive systems forsuch a tilt frame are known to those skilled in the art. The lowersurface of the tabletop 8 is directly fitted to the tilt frame. The tiltframe is located above the trend axis T-T.

Accordingly, movement of the movable framework 50 about the trend axisT-T, or when the trend axis T-T is translated upwardly or downwardly,causes corresponding movement of the tabletop 8 which is fitted to thetilt frame carried by the trend frame 50, provided by the movableframework 50, and the tilt frame can further impart additional tiltingmotion and positioning to the tabletop 8.

A first actuator mechanism 52 is coupled to the movable framework 50 andarranged to raise and lower the movable framework 50 relative to thecolumn 6 and to rotate the movable framework 50 about the trend axisT-T. The first actuator mechanism 52 is external of the column 6.

The first actuator mechanism 52 comprises first and second actuators 54,56. The first actuator 54 is connected to a first portion 58, preferablylocated at one end, of the movable framework 50 and the second actuator56 is connected to a second portion 60, preferably located at anopposite end, of the movable framework 50. The first and second portions58, 60 are mutually spaced and located on opposite sides of the trendaxis T-T and on opposite sides of the tilt axis X-X. The movableframework 50 is substantially rectangular and the first and secondportions 58, 60 are located at diagonally opposite corners 62, 64 of themovable framework 50. The movable framework 50 has a rigid frame havingopposite first and second end portions 58, 60 mutually spaced a fixeddistance.

In the embodiment, the first and second actuators 54, 56 are the onlyactuators coupled between the column 6 and the movable framework 50 forcausing movement of the movable framework 50 relative to the column 6.

The first actuator 54 has an upper first end 66 connected to the firstportion 58 of the movable framework 50. The first actuator 54 has alower second end 68 coupled to the column 6. The second actuator 56 hasan upper first end 70 connected to the second portion 60 of the movableframework 50 and a lower second end 72 coupled to the column 6. Thesecond end 68, 72 of each of the first and second actuators 54, 56 iscoupled to an external surface 74 of the column 6.

The first and second actuators 54, 56 each comprise an electric motor76, which comprises an elongate element 78 having an upper end 80connected by a pivot joint 82 to the movable framework 50 and a driveassembly 84 for extending, or retracting, the elongate element 78 so asrespectively to raise, or lower, the respective first and secondportions 58, 60 of the movable framework 50.

In the illustrated embodiment, the elongate element 78 comprises aleadscrew 86 and the drive assembly 84 is adapted to rotate theleadscrew 86 to extend, or retract, the leadscrew 86 so as respectivelyto raise, or lower, the respective first and second portions 58, 60 ofthe movable framework 50.

In an alternative embodiment, the elongate element 78 may comprise ahydraulically operated piston. Any other type of actuator may be usedthat is suitable to raise, or lower, the respective first and secondportions 58, 60 of the movable framework 50. The present invention isnot limited to any particular drive mechanism for the first and secondactuators 54, 56.

First and second stabilisers 88, 90 are also provided. Each first andsecond stabiliser 88, 90 is associated with a respective one of thefirst and second actuators 54, 56. However, in a modified embodimentonly one of the actuators is provided with a stabiliser.

The stabiliser 88, 90 comprises an extendable assembly which is fittedbetween the movable framework 50 and a lower mount pivotally coupled tothe column 6, typically the lower mount being pivotally coupled to thedrive assembly 84. An upper end of the extendable assembly is fitted toan upper end of the elongate element 78 of the respective actuator 54,56. In the illustrated embodiment, the extendable assembly and theelongate element 78 of the respective actuator 54, 56 are in parallel,but in alternative embodiments a non-parallel arrangement may beprovided.

In the illustrated embodiment, each stabiliser 88, 90 comprises a rigidelongate guide rod 92, which is parallel to the elongate element 78 ofthe respective first or second actuator 54, 56. The guide rod 92 isfitted at its upper end 83 to the respective pivot joint 82.

A hollow guide 94 slidably receives the lower portion 81 of the guiderod 92 and is pivotally coupled to the column 6. The guide rod 92 isslidable within the hollow guide 94 when the respective elongate element78 is extended or retracted. The guide rod 92 and hollow guide 94 formthe extendable assembly. The fitting between the upper end 83 of theguide rod 92 and the respective pivot joint 82 is translationally fixed,and so the guide rod 92 and its associated elongate element 78 commonlymove translationally when the elongate element 78 is extended orretracted by operation of the respective electric motor 76.

The first and second stabilisers 88, 90 function to minimise the lateralloading acting on the first and second actuators 54, 56, in particularthe elongate elements 78. The first and second stabilisers 88, 90 eachensure that the actuator loading is essentially in-line with the axis ofthe respective elongate element 78. Accordingly, buckling loads on theelongate element 78 are minimised, particularly when the elongateelement 78 is in a highly extended position which is required forcertain configurations of the movable framework 50, i.e. the trend frame50, as discussed below.

The first and second stabilisers 88, 90 also function to provide a hardend stop for the respective elongate elements 78 when the elongateelement 78 is in the most extended or most retracted configuration. Asshown in the structure of the stabilisers 88, 90, which is shown inFIGS. 10 and 11 , this is provided by stop members 91, 93 that arefitted to the guide rod 92 and are respectively urged against arespective movement limiter 95, 97 of the hollow guide 94 to define amaximum upward or downward position for the guide rod 92 relative to thehollow guide 94 and thereby limit the maximum upward extension ordownward retraction of the elongate element 78. Stop member 91 andmovement limiter 95 define a minimum-dimension contracted position forthe first and second stabilisers 88, 90 and stop member 93 and movementlimiter 97 define a maximum-dimension extended position for the firstand second stabilisers 88, 90.

One or more position sensors are located on each of the first and secondstabilisers 88, 90 to enable the translational position of the guide rod92, and thereby the associated elongate element 78, to be detected. Inthe illustrated embodiment, a contracted position sensor 99 a comprisesa magnet 201 a on an upper end of the elongate element 78 and a magneticsensor 203 a on the hollow guide 94 and an extended position sensor 99 bcomprises a magnet 201 b (shown in phantom) on a lower end of theelongate element 78 and a magnetic sensor 203 b on the hollow guide 94.The position sensors 99 a, 99 b can permit the position of the elongateelement 78 relative to an upper or lower limit to be detected.

The provision of a hard end stop and position sensors 99 a, 99 b on thefirst and second stabilisers 88, 90 rather than directly on theassociated elongate element 78, i.e. helical screw, of the first andsecond actuators 54, 56 provides the advantages as compared to knowndesigns where such functions are provided directly on the helical screw.Locating a hard end stop or position sensor on a helical screw isdifficult to implement because the screw runs through the gearbox of thedrive assembly 84 and ends stops on a helical screw may interfere withthe maximum stroke or maximum or minimum height achievable by theelongate element 78.

By locating the hard end stop and position sensors 99 a, 99 b on thefirst and second stabilisers 88, rather than on the elongate element 78,the required functions to detect and limit the position of the elongateelement 78 are achieved indirectly by detecting and controlling theassociated guide rod 92 without compromising the stroke range andfreedom of motion of the elongate element 78.

The drive assembly 84 of each first and second actuator 54, 56 ispivotally connected to the movable framework 50 by a pivot mount 51.Therefore each of the first and second actuators 54, 56, including arespective electric motor 76, elongate element 78, and drive assembly84, and a respective one of the first and second stabilisers 88, 90, isrotatable about the respective pivot mount 51.

The first and second actuators 54, 56 can be operated independently soas to be driven in the same or opposite directions. Therefore therotational orientation of the first and second actuators 54, 56 aboutthe respective pivot mount 51 can be different.

The first and second actuators 54, 56, and correspondingly therespectively associated first and second stabiliser 88, 90, are notoriented in a geometrically vertical orientation, i.e. aligned with thedirection of orientation of the column 6, but instead are inclined tothe vertical, i.e. aligned to the direction of orientation of the column6.

The elongate element 78 is linear and is inclined at an acute angle froma plane including a longitudinal axis of the column 6 and the trend axisT-T so that the upper end 80 is oriented further from the plane than alower portion 85 of the elongate element 78. The elongate elements 78 ofthe first and second actuators 54, 56 are oriented in oppositedirections from the plane. The acute angle of inclination of eachelongate element 78 from the plane decreases as the extension of theelongate element 78 increases.

The angles of the first and second actuators 54, 56 to the vertical whenextended or retracted depends on various parameters, including thelength of the actuator when extended or retracted, the horizontaldistance separating the lower pivots of the first and second actuator54, 56 (which is typically from 60 to 100 mm) and the length of themovable framework 50 between the upper pivots of the first and secondactuator 54, 56. In one embodiment, when the first or second actuator54, 56 is configured so that the respective leadscrew 86 is fullyretracted, so as to lower the respective first or second portion 58, 60of the movable framework 50, the first or second actuator 54, 56 is in afirst pivot position in which the leadscrew 86 is oriented at arelatively large acute angle (for example 10 to 25°) relative to thevertical, i.e. the direction of orientation of the column 6, the anglealso being dependent upon the height of the other actuator.

Correspondingly, in that embodiment, when the first or second actuator54, 56 is configured so that the respective leadscrew 86 is fullyextended, so as to raise the respective first or second portion 58, 60of the movable framework 50, the first or second actuator 54, 56 is in asecond pivot position in which the leadscrew 86 is extended and at arelatively small acute angle (for example 6 to 16°) relative to thevertical, i.e. the direction of orientation of the column 6, the anglealso being dependent upon the height of the other actuator.

When the first and second actuators 54, 56 are both fully retracted inthat embodiment, each leadscrew 86 is oriented at an acute angle of from18 to 25° relative to the vertical. When the first and second actuators54, 56 are both fully extended in that embodiment, each leadscrew 86 isoriented at an acute angle of from 12 to 17° relative to the vertical.When one of the first and second actuators 54, 56 is fully extended andthe other of the first and second actuators 54, 56 is fully retracted,the extended leadscrew 86 is oriented at an acute angle of from 5 to 8°relative to the vertical and the retracted leadscrew 86 is oriented atan acute angle of from 9 to 13° relative to the vertical.

The movable framework 50 defines an internal opening 98 which is largerthan an upper end 100 of the column 6. The first actuator mechanism 52is capable of lowering the movable framework 50 relative to the column 6to a lowermost position in which the movable framework 50 is below theupper end 100 of the column 6 and annularly surrounds the column 6. Inthe lowermost position the trend axis T-T is below the upper end 100 ofthe column 6, and extends through an upper part of the outer columnelement 30 which surrounds the inner column element 34 when the columnelements 30, 32, 34 are telescoped into the contracted configuration,and typically the movable framework 50 is entirely below the upper end100 of the column 6.

The first actuator mechanism 52 is capable of raising the movableframework 50 relative to the column 6 to an uppermost position in whichthe movable framework 50 is above the upper end 100 of the column 6. Inthe uppermost position the trend axis T-T is above the upper end 100 ofthe column 6, and is spaced by a spacing height from an uppermost partof the column 6, and typically the movable framework 50 is above,preferably entirely above, the upper end 100 of the column 6. The firstactuator mechanism 52 is fitted to the outer column element 30 and whenthe column elements 30, 32, 34 are telescoped into an extendedconfiguration the first actuator mechanism 52, the movable framework 50and the tabletop 8 are raised relative to the base 4.

In the illustrated embodiment two linear guide mechanisms 102 areprovided on opposite sides of the column 6. Each linear guide mechanism102 extends along at least a part of the column 6. Each linear guidemechanism 102 comprises a first part 104 coupled to the column 6 and asecond part 106 coupled to the movable framework 50. Each linear guidemechanism 102 comprises a respective pair of first and second parts 104,106.

The first and second parts 104, 106 are relatively movable along alinear axis L-L, shown in FIG. 5 , of the linear guide mechanism 102 toenable the movable framework 50 to be translated along the linear axisL-L by relative movement of the first and second parts 104, 106. Thefirst part 104 is a fixed linear guide member 110, fixed to the column6, and the second part 106 is a movable linear guide member 112, coupledto the movable framework 50 at a trend pivot 118. The first part 104 isan elongate channel 114 and the second part 106 is an elongate slider116 within the channel 114, although the opposite configuration may beemployed.

In the illustrated embodiment, the two linear guide mechanisms 102 areraised or lowered synchronously with the raising or lowering of thetrend pivots 118. The two linear guide mechanisms 102 ensure that thetrend pivots 118 can only move vertically.

Optionally, the linear guide mechanisms 102 may be provided with alocking mechanism to lock the linear guide mechanism 102 at a selectedheight, and thereby lock the trend pivots 118, and the trend axis T-T,at a selected height.

Additionally or alternatively, the linear guide mechanisms 102 may beprovided with a braking mechanism which can be activated to brake themovement of the linear guide mechanisms 102. Both the locking mechanismand the braking mechanism act to take at least a proportion of theapplied tabletop load from the first and second actuators 54, 56.

The locking and/or braking mechanism may be an electric actuator, ahydraulic cylinder or a locking gas spring, all of which constructionsare known to those skilled in the art.

Referring additionally to FIG. 4 , a brace mechanism 108 is coupled to,and mounted between, the pair of linear guide mechanisms 102. The bracemechanism prevents twisting of the trend pivot 118 and the associatedlinear guide mechanisms 102. The brace mechanism 108 comprises a braceelement 120 having a central plate member 122 and two opposite end platemembers 124, 126 that are orthogonal to the central plate member 122 andoriented in a common direction. A free end 128 of each end plate member124, 126 is rigidly affixed, for example by bolts or screws, to arespective movable linear guide member 112, and thereby coupled to themovable framework 50.

The brace mechanism 108 functions to connect together the pair of linearguide mechanisms 102 for the trend pivot so that the movable framework50 does not twist when under a high applied mechanical load, for exampleparticularly when a heavy patient is on the tabletop 8. The bracemechanism 108 ensures that the two opposite linear guide mechanisms 102are located at the identical height.

A twisting force applied to the movable framework 50, i.e. the trendframe 50, at least partly about an axis extending orthogonal to thetrend axis T-T, acting for example to urge one lateral side of themovable framework 50 downwardly relative to the opposite lateral side ofthe movable framework 50, is resisted by the brace mechanism 108. Theplate members 122, 124, 126 are typically composed of heavy gauge steelso as to exhibit high rigidity and resistance to shear forces in theplane of the respective plates.

In a preferred modification to increase the rigidity of the bracemechanism 108, as shown in FIG. 12 the central plate member 122 ismovably fitted to the column 6 by one or more linear brace guides 121which extend along the column 6. Each linear brace guide 121 has a fixedlinear brace guide member 123, fixed to the column 6, and a movablelinear brace guide member 125, coupled to the movable framework 50. Themovable linear brace guide member 125 is an elongate channel 130 and thefixed linear brace guide member 123 is an elongate slider 132 within thechannel 130, although the opposite configuration may be employed.

The first actuator mechanism 52 is fitted to an external surface 136 ofthe outer column element 30. The linear guide mechanisms 102, and whenpresent the one or more linear brace guides 124, are also fitted to theouter column element 30, in particular to the external surface 136 ofthe outer column element 30. When the column elements 30, 32, 34 aretelescoped into an extended configuration, the linear guide mechanisms102 and the brace mechanism 108 are raised relative to the base 4.

The movable framework 50, and consequently the tabletop 8 thereon, issupported on the column 6 (i) by the first and second actuators 54, 56and the respective associated stabilisers 88, 90 and (ii) by the linearguide mechanisms 102 and the associated brace mechanism 108. In order toprovide enhanced resistance of the surgical table 2 to twisting forceswhich may be encountered in use, rather than over-strengthening theactuators 54, 56, stabilisers 88, 90, linear guide mechanisms 102 and/orbrace mechanism 108, which would enlarge the weight and dimensions ofthe column and would reduce the ability of the column to be contractedto a low height, and increase component costs, the surgical table 2 ispreferably provided with a further twist-resisting mechanism. Thetwist-resisting mechanism may comprise a connection between at least oneof the actuator/stabiliser assemblies and the column 6 at a locationbetween the upper and lower ends of the actuator/stabiliser assembly sothat twisting of the actuator/stabiliser assembly relative to the column6 is prevented or at least minimised. One embodiment of atwist-resisting mechanism is shown in FIGS. 1 to 6 and 9 .

Referring to FIG. 9 , to provide a twist-resisting mechanism 900 atleast one of the hollow guides 94, forming a stabiliser body, isslidably and rotatably connected to the column 6 via pin bearing member901 on the hollow guide 94. The pin bearing member 901 is slidablyreceived in an arc-like slot 902 in a bracket 903 that is fitted to thecolumn 6. This provides a slot and bearing arrangement 904 to allow thestabiliser body and the associated actuator to rotate about a horizontalaxis at pivot mount 51 but prevents torsional rotation of the stabiliserbody and the associated actuator and rotation of the stabiliser body andthe associated actuator about any other axis.

The slot and bearing arrangement 904 provides a reinforcement againsttwisting within the tabletop 8 that may be created by anoperator-applied load acting on the side of the table 2. The slot andbearing arrangement 904 also minimises any buckling load acting on thestabilisers 88, 90 and elongate elements 78 of the first and secondactuators 54, 56.

As shown in FIGS. 14 a and 14 b , the locking and/or braking mechanism101 comprises an assembly of two oppositely oriented vertically orientedgas springs 801 a, 801 b. A first, lower, gas spring 801 a has a freeend 803 a of a piston element 804 a pivotally fitted to the bracemechanism 108 by a rigid plate 805 fixed to, and extending downwardlyfrom, the brace mechanism 108. A second, upper, gas spring 801 b has afree end 803 b of a piston element 804 b pivotally fitted to the column6. Each gas spring 801 a, 801 b has a respective cylinder element 802 a,802 b. The two cylinder elements 802 a, 802 b are connected to eachother so as to be fixed together in a vertical direction. The twocylinder elements 802 a, 802 b may optionally additionally be (i)slidably fitted to the brace mechanism 108 or the column 6 by a slidingjoint (not shown) and/or (ii) guided by a guide device (not shown), ineach case to ensure vertical motion of the gas springs 801 a, 801 b andprevent lateral deflection of the assembly of two oppositely orientedvertically oriented gas springs 801 a, 801 b when under load.

In the illustrated embodiment the locking and/or braking mechanism 101is fitted directly to the brace mechanism 108 and thereby indirectly tothe linear guide mechanisms 102 to which the brace mechanism 108 iscoupled. In an alternative embodiment, the locking and/or brakingmechanism 101 is fitted directly to one or both of the linear guidemechanisms 102. In each embodiment, the locking and/or braking mechanism101 can provide a locking and/or braking function between the movableframework 50, and thereby the tabletop 8, and the column 6.

FIG. 14 a illustrates the position and configuration of the gas springs801 a, 801 b when the movable framework 50 is at maximum height relativeto the column 6. The brace mechanism 108 is in a high position and thegas springs 801 a, 801 b are both fully contracted. FIG. 14 billustrates the position and configuration of the gas springs 801 a, 801b when the movable framework 50 is at minimum height relative to thecolumn 6. The brace mechanism 108 is in a low position and the gassprings 801 a, 801 b are both fully extended.

The gas springs 801 a, 801 b may be controlled in known manner, forexample by a solenoid control, to provide: a braking function fordownward or upward movement of the movable framework 50 relative to thecolumn 6; a lift function for raising the movable framework 50 relativeto the column 6; and/or a locking function for locking the position ofthe movable framework 50 relative to the column 6. The double gas springarrangement can provide a low contracted height and a high stroke,corresponding with the movement range of the movable framework 50 andthe column 6.

Other locking and/or braking mechanisms will be apparent to thoseskilled in the art. For example, a single gas spring and solenoidactuator assembly may be provided between the movable framework and thecolumn, and/or a rail clamp may be provided on the brace mechanism forselectively clamping, using an actuator, to one or more rails fitted tothe column.

When the locking and/or braking mechanism 101 is configured to provide alift function, the locking and/or braking mechanism 101 may comprise asecond actuator mechanism coupled to the linear guide mechanism 102 andarranged to cause relative movement of the first and second parts 104,106 thereby to raise and lower the trend axis T-T relative to the column6.

In the surgical table 2 of the illustrated embodiment, a lifting andorienting mechanism for the trend frame 50, which is movable framework50, is fitted around the outside of the column. The lifting andorienting mechanism comprises the first actuator mechanism 52, which inturn comprises the first and second actuators 54, 56. The first andsecond actuators 54, 56 can have a ballscrew or leadscrew construction.

Each respective electric motor 76 drives the respective elongate element78 through a gearbox in the electric motor 76. The first and secondactuators 54, 56 are positioned so that the trend frame 50 is supportedon opposite sides of the column 6, each side extending transverse to thetrend axis T-T and constituting a “front” or “rear” side of the column 6as would be understood by those skilled in the art, at diagonallyopposite corners of the trend frame 50.

The linear guide mechanisms 102 on opposite sides of the column 6 allowthe central trend pivot axis T-T to be raised and lowered and act astrend pivot guides. The opposite trend pivots 118 are mounted to thelinear guide mechanisms 102 and can move vertically along the directionof the column 6, guided by the linear guide mechanisms 102.

The brace mechanism 108 connects together the trend pivot guides. Thebrace mechanism 108 may have sufficient stiffness and resistance totwisting to brace the opposite trend pivots 118 so that the oppositetrend pivots 118 are maintained at exactly the same height, although thestiffness may be enhanced by at least one linear brace guide 124 betweenthe brace mechanism 108 and the column 6. The trend frame 50 pivotsabout the opposite trend pivots 118 and is located between the first andsecond actuators 54, 56 and the tilt frame. The trend frame 50 has ahigh degree of freedom of motion, as described in further detail below.

The operation of the surgical table 2 will now be described.

As described above, the surgical table 2 incorporates a mechanism forcontrolling the trend angle and height of a trend frame 50, which isbeneath the tabletop 8. The trend frame 50 can be rotated about a trendaxis, and the angle of inclination of the trend frame 50 sets the trendangle of the tabletop 8. The height of the column 6 can be controlledindependently from the height of the trend frame 50.

FIGS. 2 b and 4 show the column 6 at minimum height and the movableframework 50, constituting the trend frame 50, at maximum height. Inthis configuration, the elongate elements 78 of the first and secondactuators 54, 56 and the first and second stabilisers 88, 90 areextended (and these elements are fully extended at 45 degreetrend/reverse trend angles). In this configuration, the linear guidemechanisms 102 are fully extended, to provide the brace mechanism 108 ina fully raised position. The first and second stabilisers 88, 90 and thebrace mechanism 108 prevent twisting of the movable framework 50 underthe action of any applied load on the table 2.

The trend axis T-T is raised relative to the column 6. The movableframework 50 is raised relative to the column 6 to an uppermost positionin which the movable framework 50 is above the upper end 100 of thecolumn 6, the trend axis T-T is above the upper end 100 of the column 6,and the movable framework 50 is entirely above the upper end 100 of thecolumn 6. The column elements 30, 32, 34 are telescoped into acontracted configuration. The movable framework 50 and the tabletop 8are raised relative to the base 4 by the first and second actuators 54,56.

In this configuration, the trend axis T-T is typically 410 mm above thebottom of the column 6 which is mounted on the base 4. Thisconfiguration could be used as a rest position for the surgical table 2.

When it is desired to lower the tabletop 8 even further, for example totransfer a patient onto or from the tabletop 8, the movable framework 50can be lowered even further, which lowers the tabletop 8 supportedthereby.

Accordingly, FIGS. 2 a and 3 shows the column 6 at minimum height andthe movable framework 50, constituting the trend frame 50, at minimumheight. In this configuration, the elongate elements 78 of the first andsecond actuators 54, 56 are fully retracted.

The trend axis T-T is lowered relative to the column 6. The movableframework 50 is lowered relative to the column 6 to a lowermost positionin which the movable framework 50 is below the upper end 100 of thecolumn 6 and annularly surrounds the column 6. In the lowermost positionthe trend axis T-T is below the upper end 100 of the column 6 andextends through an upper part of the outer column element 30 and themovable framework 50 is entirely below the upper end 100 of the column6.

In this configuration, the trend axis T-T is typically 290 mm above thebottom of the column 6 which is mounted on the base 4 and the columnheight is typically less than 380 mm above the base 4.

When it is desired to incline the tabletop at a trend angle, as shown inFIG. 5 the column 6 can be set at its minimum height, as describedabove, and the trend frame 50 can be set at an intermediate height, andwith the trend frame 50 at a forward or reverse trend angle of up to45°. The trend angle may be controlled by providing that one of theelongate elements 78 of the first and second actuators 54, 56 isretracted (in FIG. 5 , second actuator 56) and the other of the elongateelements 78 of the first and second actuators 54, 56 (in FIG. 5 , firstactuator 54) is extended.

At the maximum trend angle of +45° or −45° (or even greater trend anglevalues) one of the elongate elements 78 of the first and secondactuators 54, 56 is fully retracted and the other of the elongateelements 78 of the first and second actuators 54, 56 is fully extended.This provides a large range of trend angles, over an angular range of90°, from endpoints of +45° to −45° even when the column 6 is fullyretracted, and so the tabletop 8 is at a relatively low height, with thetrend axis typically being no more than 410 mm above the base 4.

FIG. 6 shows the fully extended column 6 at maximum height and themovable framework 50 of the trend frame 50 also at maximum heightrelative to the column 6. In this configuration, the elongate elements78 of the first and second actuators 54, 56 are extended (and theseelements are fully extended at 45 degree trend/reverse trend angles). Inthis configuration, the linear guide mechanisms 102 are fully extended,to provide the brace mechanism 108 in a fully raised position. The trendaxis T-T is raised relative to the column 6 to the uppermost position asdescribed above.

In this configuration, the trend axis T-T is typically 945 mm above thebottom of the column 6 which is mounted on the base 4.

The above-described lifting and orienting mechanism for the trend frame50 permits a number of different motions which can be selected by theuser by controlling the first and second actuators 54, 56. Theparticular structural relationship between the first and secondactuators 54, 56 and the trend frame 50 achieves a remarkable varietyand range of motions of the trend frame 50.

The trend frame 50, and therefore the tabletop 8, can be rotated intoeither reverse trend or trend by driving either each of the first andsecond actuators 54, 56 individually or both of the first and secondactuators 54, 56 at the same time in opposite directions, depending uponthe initial position of the trend axis T-T relative to the column 6.Operating two trend actuators together has the benefit of increasing thespeed of trend movement as a result of a reduction in the distance thateach trend actuator, namely the first and second actuators 54, 56, hasto drive for any given change in trend or reverse trend angle.

In particular, the trend frame 50 can be raised or lowered, with thetrend frame at any given orientation, for example level, i.e.horizontally oriented. This function is achieved by driving both of thefirst and second actuators 54, 56 simultaneously in the same direction,i.e. extending to raise elongate element 78 or retracting to lowerelongate element 78, and at the same translational rate. The position ofthe trend axis T-T is correspondingly raised or lowered, which raises orlowers the brace mechanism 108 coupled to the pair of linear guidemechanisms 102 fitted to the outer column element 30 of the extendablecolumn 6.

The trend frame 50 can therefore be raised or lowered relative to theouter column element 30 of the column 6, and, independently therefrom,the outer column element 30 can be raised or lowered relative to thebase 4 of the surgical table 2 since the column 6 is extendable. Thecumulative effect is that the vertical motion of the trend frame 50relative to the base 4 of the surgical table 2 can combine the verticalmotion of the trend frame 50 relative to the column 6 in an additivesense with vertical motion of the extendable column 6.

The total range of vertical motion of the trend frame 50 relative to thebase 4 of the surgical table 2 is very high, and higher than knownsurgical tables. Consequently, the lowermost position of the tabletop 8is very low, and the highest position is very high, as compared to knownsurgical tables.

In addition, the trend frame 50 can be raised or lowered so as to orientthe trend frame at any given orientation relative to the horizontal,i.e. to a reverse trend orientation (with the lower torso section 16coupled to the trend frame 50 inclined so that the head section 12 ofthe tabletop 8 is above the leg sections 18 of the tabletop 8) or to atrend orientation (with the lower torso section 16 coupled to the trendframe 50 inclined so that the head section 12 of the tabletop 8 is belowthe leg sections 18 of the tabletop 8). This function is achieved,depending upon the start position of the tabletop 8 and the trend frame50, by driving one or both of the first and second actuators 54, 56.

For example, if the tabletop 8 and the trend frame 50 are initiallylevel relative to the horizontal, as shown in FIG. 7 a , the first andsecond actuators 54, 56 can be driven simultaneously in oppositedirections, i.e. extending to raise one elongate element 78 andretracting to lower the other elongate element 78, and at the sametranslational rate, which may be termed a symmetric mode to achieve areverse trend position as shown in FIG. 7 b or a trend position as shownin FIG. 7 c.

When the first and second actuators 54, 56 are driven simultaneously inopposite directions, the vertical position of the trend axis T-T isstationary, and the trend frame 50 rotates about the trend axis T-T.Driving the first and second actuators 54, 56 simultaneously in oppositedirections, provides the advantage that very fast trend, or reversetrend, movement can be achieved. The enhanced speed is achieved sinceboth sides of the trend frame 50 are raised or lowered relative to thetrend axis T-T, and so the translational distance that each of the firstand second actuators 54, 56 need to extend or retract is minimised for agiven change in trend angle. The reduced actuator driving distance for agiven change in trend angle permits faster trend movement.

It is very desirable for the surgical table to reduce the time period toachieve a trend position, for example from a horizontal position, sincein many surgical procedures it may be necessary in an emergency to putthe surgical table into a trend position to maximise blood flow to thepatient's head as quickly as possible.

Alternatively, the trend frame 50 can be raised or lowered so as toorient the trend frame at any given orientation relative to thehorizontal, i.e. to a reverse trend orientation or to a trendorientation by driving only one of the first and second actuators 54,56, or by driving both of the first and second actuators 54, 56 in anasymmetric mode, i.e. the first and second actuators 54, 56 are drivenin other than an opposite and simultaneous manner.

For example if the tabletop 8 and the trend frame 50 are initially levelrelative to the horizontal, and the tabletop 8 is at a minimum height,as shown in FIG. 8 a , the second actuator 56 can be undriven so thatits elongate element 78 is stationary, and remains retracted, and thefirst actuator 54 can be driven in an upward direction, i.e. extendingto raise its elongate element 78, as shown in FIG. 8 b . The pivot joint82 of the second actuator 56 thereby defines the effective trend axisT1-T1 for the trend frame 50. The central trend axis T-T iscorrespondingly raised relative to the effective trend axis T1-T1 andthe rotational motion of the trend frame 50 is about the effective trendaxis T1-T1 rather than the central trend axis T-T.

Conversely, as shown in FIG. 8 c if the first actuator 54 is undriven,and remains retracted, and the second actuator 56 is driven to extendthe elongate element 78, the pivot joint 82 of the first actuator 54thereby defines a second effective trend axis T2-T2 for the trend frame50. Furthermore, the trend or reverse trend position can be achieved bylowering one of the first and second actuators 54, 56 and keepingstationary the other of the first and second actuators 54, 56.

It may be seen that by providing a mounting for the central trend axisT-T which can move vertically, by vertical motion of the opposite trendpivots 118 which are mounted to the linear guide mechanisms 102, and byproviding that the first and second actuators 54, 56 can be drivenentirely independently, the effective trend axis, i.e. the axis that thetrend frame 50 actually pivots about during a trend or reverse trendmotion, can be selectively located at one of three positions, namely thetrend pivots 118 (defining trend axis T-T), the pivot joint 82 of thesecond actuator 56 (defining trend axis T1-T1) or the pivot joint 82 ofthe first actuator 54 (defining trend axis T2-T2).

Yet further, as shown in FIG. 9 , if both of the first and secondactuators 54, 56 are driven simultaneously but other than both (i) inopposite directions and (ii) simultaneously, then the effective trendaxis 200, i.e. the axis that the trend frame 50 actually pivots aboutduring a trend or reverse trend motion, can be virtually located at anyposition between the pivot joint 82 of the first actuator 54 (T2-T2) andthe pivot joint 82 of the second actuator 56 (T1-T1). For example if thefirst actuator 54 is raised at a velocity of X m/s and the secondactuator 56 is lowered at a velocity of −2X m/s, the effective trendaxis 200 is virtually located at a position between the trend pivots 118and the pivot joint 82 of the second actuator 56 (T1-T1).

It may therefore be seen that by varying the relative velocity anddirection of motion of the first and second actuators 54, 56, thelocation of the effective trend axis, which may be at a physical pivotor at a virtual pivot, can be at any position from, and including, thephysical pivot joint 82 of the first actuator 54 (defining trend axisT2-T2) to, and including, the physical pivot joint 82 of the secondactuator 56 (defining trend axis T1-T1), and may be at the physicaltrend pivots 118 (defining trend axis T-T), or any position therebetweenas a virtual pivot.

A control mechanism 150, illustrated schematically in FIG. 1 as awireless control, may be provided to cause the height of the effectivetrend axis to be variable within a first dimensional range and to causethe location of the effective trend axis in a direction orthogonal tothe transverse axis to be variable within a first dimensional range.

By providing an ability to select the location of the effective trendaxis across the length of the trend frame 50, i.e. in a direction alongthe central axis C-C, the relationship between the trend/reverse trendorientations and height of the tabletop 8 has a very high freedom ofmovement.

For example, if the tabletop 8 is initially in a medium heighthorizontal position, the tabletop 8 can be driven to a trend positionvery quickly by simultaneously driving the first and second actuators54, 56 in opposite directions, which lowers the head and raises the feetof the patient, and the effective trend axis would be at the physicaltrend pivots 118 (defining trend axis T-T).

However, if the tabletop 8 is initially in a low height horizontalposition, it may not be possible further to lower the head to a trendposition simply by rotating the trend frame 50 about the central trendaxis T-T defined by the trend pivots 118, because the head section 12may already be at its minimum height.

Therefore, the tabletop 8 can be driven to a trend position quickly byonly driving the first actuator 54 and by keeping the second actuator 56stationary. This inclines the entire tabletop 8, and raises the feet ofthe patient, but keeps the head of the patient at substantially the sameheight relative to the floor. The effective trend axis would be at thephysical pivot joint 82 of the second actuator 56 (defining trend axisT1-T1).

This provides the advantage that the tabletop 8 can quickly attain atrend position from a low initial height merely by tilting the tabletopabout a selected non-central trend axis and without requiring the entiretabletop to be raised in height; in contrast, in known surgical tablesit would be necessary to raise the entire tabletop relative to the floorto achieve a trend position from an initial low tabletop startingposition, which would delay and slow down the trend operation.

Conversely, if the tabletop 8 is initially in a high height horizontalposition, and it is possible further to lower the head towards the floorinto a trend position, the trend frame 50 may be rotated about aneffective trend axis at the physical pivot joint 82 of the firstactuator 54 (defining trend axis T2-T2), because the leg sections 18 mayalready be at their maximum height. Therefore, the tabletop 8 can bedriven to a trend position quickly by only driving the second actuator56 and by keeping the first actuator 54 stationary.

It should be clear that any non-symmetric simultaneous motion of thefirst and second actuators 54, 56 can locate the effective trend axis atany physical or virtual pivot in the distance extending from thephysical pivot joint 82 of the first actuator 54 to the physical pivotjoint 82 of the second actuator 56, which further enhances theversatility, with regard to height and speed, of achieving thetrend/reverse trend orientations of the tabletop 8.

Of course, this versatility is further enhanced by providing the liftingand orienting mechanism for the trend frame 50 on the extendable column6 which can be independently driven from the first and second actuators54, 56 which drive the trend frame 50.

Consequently, the versatility, with regard to height and speed, ofachieving the trend/reverse trend orientations of the tabletop 8 aresignificantly higher than as compared to known surgical tables.

FIGS. 12 and 13 show that the footprint 700 of the column 6, and themechanism for controlling the trend angle and height of the trend frame50, is small when the column and the mechanism are fully retracted. Thefootprint of the combination of both the column 6 and the first andsecond actuators 54, 56 typically has a length (along the longitudinalaxis of the tabletop 8) of 330 mm or less and a width (along thetransverse axis of the tabletop 8) of 305 mm.

FIGS. 15, 16 and 17 a and 17 b illustrate a cable management system forthe column 6. FIG. 15 illustrates the column in a contractedconfiguration and FIG. 16 illustrates the column in an extendedconfiguration, and the cable management system 300 is configured to beretractable and extendable corresponding to the column 6 without causinga kinking and damage to cables within the cable management system 300.FIGS. 17 a and 17 b schematically illustrate the cable configurationwhen the column 6 is in the contracted or extended configurationrespectively.

In the surgical table 2, power and control cables 302 need to beconnected between the base 4 and the tabletop 8. The cables 302 extendup the column 6 from the base 4 to be connected as required within thetabletop 8.

A pair of flexible chain cable guides 304, 306 are provided. A firstcable guide 304 has a first end portion 308 fitted, directly orindirectly, to the base 4 and a second end portion 310 fitted, directlyor indirectly, to the intermediate column element 32 (or oneintermediate column element 32 if there are plural telescopedintermediate column elements). A second cable guide 306 has a first endportion 312 fitted, directly or indirectly, to the intermediate columnelement 32 and a second end portion 314 fitted, directly or indirectly,to the outer column element 30.

The first end portion 308 of the first cable guide 304 is connected to alower elongate bracket 316, which includes one or more fitting holes 317for fitting the lower elongate bracket 316 to the base 4 by screws. Thelower elongate bracket 316 defines an elongate guide slot 318 which isupwardly oriented and within which first end portion 308, and theadjacent portion of the first cable guide 304, are received. The lowerelongate bracket 316 is fitted, directly or indirectly, to the base 4.

The second end portion 310 of the first cable guide 304 is connected toa centre bracket 320 from which extends an elongate wall 322 which isupwardly oriented. The centre bracket 320 is fitted, directly orindirectly, to a lower part 324 of the intermediate column element 32.The second end portion 310, and the adjacent portion of the first cableguide 304, can be aligned against one face 326 of the elongate wall 322.

The first end portion 312 of the second cable guide 306 is connected tothe centre bracket 320 on an opposite side from the second end portion310 of the first cable guide 304. The first end portion 312, and theadjacent portion of the second cable guide 306, can be aligned againstthe opposite face 328 of the elongate wall 322.

The second end portion 314 of the second cable guide 306 is connected toa higher bracket 330 which is fitted, directly or indirectly, to a lowerpart 332 of the outer column element 30. The higher bracket 330 definesa guide slot 334 which is upwardly oriented and within which second endportion 314 is received. The guide slot 334 of the higher bracket 330 isshorter than the elongate guide slot 318 of the lower elongate bracket316.

The first and second cable guides 304, 306 each comprise a flexiblechain 336 which is formed of a plurality of linked elements 338. Theelements 338 each have a central channel portion 340 so that theresultant flexible chain 336 has a central elongate channel 342 alongits length. One or more cables 302 is received in the elongate channel342.

The cables 302 from the base 4 enter the first end portion 308 of thefirst cable guide 304, exit the second end portion 310 of the firstcable guide 304 in the vicinity of the centre bracket 320, then enterthe first end portion 312 of the second cable guide 306 and exit thesecond end portion 314 of the second cable guide 306 to be connected tothe tabletop 8.

As shown in FIG. 15 , In the vicinity of the centre bracket 320, thecables 302 hang down as a downwardly depending loop 344 from the centrebracket 320. The downwardly depending loop 344 is located at asubstantially central position across a lateral width of the cablemanagement system 300. The pair of flexible chain cable guides 304, 306therefore provide that the cables 302 are secured in a fixed loop 344 atthe central position 321, provided by the centre bracket 320, of thecable management system 330 where the cables connect together the twoflexible chain cable guides 304, 306.

A generous bend radius can be provided at this central position 321which can be equivalent to the bend radii provided at the top of eachupwardly extending loop 345, 347 of the respective flexible chain cableguides 304, 306. A typical width of the cable management system 330 isabout 180 mm.

As shown in FIG. 17 a , in the contracted configuration of the column 6,the cables 302 have three large radius bends at loops 344, 345 and 347and the cables 302 are fixed at three points corresponding to the lowerelongate bracket 316, the centre bracket 320 and the higher bracket 330.The cables 302 generally form an m-shape. The central part of the cables302 is guided by the centre bracket 320.

As shown in FIG. 17 b , in the extended configuration of the column 6,the cables 302 still have three large radius bends at loops 344, 345 and347. The cables 302 generally form a stepped m-shape. The central partof the cables 302 remains guided by the centre bracket 320.

As compared to a typical conventional S-shape arrangement for the cablesextending up a column of a surgical table, in which the cables are notdirectly supported at the centre of the S-shape, the central bracketprevents the cables and associated cable guides from sagging at thecentral position. This minimises stress at the central position, as thecentral position is driven by the column and therefore the cables arefully supported at the centre. This also reduces cable stress at the toploop 347.

In the illustrated embodiment, first and second cable guides 304, 306are provided and these may be provided by two individual cable guidesthat intersect at the centre bracket 320, or alternatively a singlecable guide member is provided which is bent at the centre bracket 320to form the first and second cable guides 304, 306.

The first and second cable guides 304, 306 are composed of a polymer,for example polypropylene. These cable guides are known in the art, anda suitable cable guide is sold on commerce under the trade mark “energyChain®” by Igus (UK) Limited of Northampton, UK.

In the contracted configuration the first and second cable guides 304,306 are laterally adjacent, and form a shape of an inverted W, and thecable management system 300 has a minimum total height, and in theextended configuration the second cable guide 306 is substantially abovethe first cable guide 304 and the cable management system 300 has amaximum total height.

As shown in FIG. 15 , when the column 6 is in the contractedconfiguration, each of the first and second cable guides 304, 306 is ina contracted configuration and has a minimum total height. Also, sincethe first and second cable guides 304, 306 are in a side-by-sideconfiguration because the lower part 324 of the intermediate columnelement 32 and the lower part 332 of the outer column element 30 arealigned and adjacent to the base 4, the total height of the entire cablemanagement system 300 is minimised.

As shown in FIG. 17 a , the first and second cable guides 304, 306 areeach configured to be, in the contracted configuration, in the form ofan inverted U, and thereby have substantially parallel pairs of uprightopposed legs 346, 348 and 350, 352 of substantially the same length.Each pair of legs 346, 348 and 350, 352 is interconnected at therespective upper ends 354, 356 by a transverse interconnection 358, 360.In the illustrated embodiment, in which the column 6 has a contractedheight of typically less than 380 mm, the first and second cable guides304, 306 each have a contracted height of typically 250 mm.

In the contracted configuration, the elongate guide slot 318 of thelower elongate bracket 316, the elongate wall 322 of the centre bracket320, and the guide slot 334 of the higher bracket 330 all assist thefirst and second cable guides 304, 306 assuming the desired contractedconfiguration of minimum total height and with the first and secondcable guides 304, 306 being each configured in the form of an invertedU. This avoids damage and kinking of the cables in the contractedconfiguration.

As shown in FIGS. 16 and 17 b, in contrast, when the column 6 is in theextended configuration, each of the first and second cable guides 304,306 is in an extended configuration and has a maximum total height. Thefirst and second cable guides 304, 306 are each configured in the formof an inverted J. The opposed legs 346, 348 and 350, 352 of each pairhave different length. In the first cable guide 304, the leg 346connected to the base 4 is longer than the leg 348 connected to theintermediate column element 32. In the second cable guide 306, the leg350 connected to the intermediate column element 32 is longer than theleg 352 connected to the outer column element 30.

In the illustrated embodiment, in which the column 6 has a contractedheight of typically less than 380 mm, the total extended height from thecable entrance 362 of the first cable guide 304 at first end portion 308to the cable exit 366 from the second cable guide 306 at second endportion 314 is typically 525 mm.

In the extended configuration, the elongate guide slot 318 of the lowerelongate bracket 316, the elongate wall 322 of the centre bracket 320,and the guide slot 334 of the higher bracket 330 again all assist thefirst and second cable guides 304, 306 assuming the desired extendedconfiguration of maximum total height and with the first and secondcable guides 304, 306 being each configured in the form of an inverted Jwith substantially parallel legs. Again, this avoids damage and kinkingof the cables in the extended configuration, and when transitioningbetween the extended configuration and the contracted configuration.

The lower elongate bracket 316, the centre bracket 320, and the higherbracket 330 are typically composed of sheet metal. These bracketsprevent excess cable pressure, otherwise generated by the spring tensionin the cables, particularly when the cables are bent around a tightradius. Such excess cable pressure would cause unwanted lateral movementand sagging of the first and second cable guides 304, 306.

The cable management system 330 enables a low contracted height to beachieved in combination with a high stroke. The cables can be connectedfrom the base 4 to the top section of the column 6 without requiring thecables to extend upwardly along the full contracted height of thecolumn.

In the extended position, the cables connect securely to the top element30 of the column 6 but the uppermost part of the cable management system300 remains located a distance significantly below the upper end 100 ofthe column 6.

This assists minimising the footprint of the column 6 and assistspermitting clearance for other table components, particularly the trendframe 50, in extreme trend positions.

In an alternative embodiment of the present invention, as illustrated inFIG. 18 , instead of the brace mechanism there is provided a secondactuator mechanism 408 which is coupled to the linear guide mechanism102. The brace mechanism is passive and unpowered, and in thatembodiment the power for lifting and tilting the trend frame 50 isprovided by the first and second actuators.

In the embodiment comprising the second actuator mechanism 408, thesecond actuator mechanism 408 is active and powered, and in thisembodiment additional power, additional to that provided by the firstand second actuators, for lifting and tilting the trend frame 50 isprovided by the second actuator mechanism 408.

Although only one linear guide mechanism 102 may optionally be provided,in the illustrated embodiment the second actuator mechanism 408 isarranged to cause relative movement of the first and second parts 104,106 thereby to raise and lower the trend axis T-T relative to the column6. Like the first actuator mechanism 52, the linear guide mechanism 102and second actuator mechanism 408 are external of the column 6. Thesecond actuator mechanism 408 comprises a pivotable arm 418 having afirst end 420 pivotally attached to the second part 106 and a second end422 pivotally coupled to a third linear actuator 424. The arm 418 ispivoted about a pivot 426 located between the first and second ends 420,422 and fixed to the column 6. A pin 428 is mounted on the second part106 and the first end 420 has a slot 430 in which the pin 428 isreceived. The pin 428 is slidable along the slot 430 when the arm 418 ispivoted about the pivot 426.

In the illustrated embodiment two linear guide mechanisms 102 areprovided on opposite sides of the column 6, and correspondingly thesecond actuator mechanism 408 comprises two pivotable arms 418, eachpivotable arm 418 being attached to a respective second part 106 andcoupled to the third linear actuator 424. The second end 422 of eachpivotable arm 418 is pivotally coupled to the third linear actuator 424by a drive rod 432 which is pivotally fitted between the second ends422. The drive rod 432 is pivotally fitted to a movable end 434 of anelongate linear drive member 436 of the third linear actuator 424.

The arrangement is such that linear movement of the third linearactuator 424 causes rotation of the arm 418 about the pivot 426 andmovement of the second part 106 thereby to raise and lower the trendaxis T-T relative to the column 6. Typically, the second actuatormechanism 408 incorporates a locking mechanism for locking the trendaxis T-T at a selected height position relative to the column 6, thelocking mechanism being incorporated within the third linear actuator424.

When it is desired to raise the trend axis T-T relative to the column 6,the elongate linear drive member 436 of the third linear actuator 424 isretracted so that the pivotable arms 418 are rotated (in a clockwisedirection in the Figure) to push up the movable linear guide member 112,coupled to the movable framework 50 at the trend pivot.

When it is desired to lower the trend axis T-T relative to the column 6,the elongate linear drive member 436 of the third linear actuator 424 isextended so that the pivotable arms 418 are rotated (in ananti-clockwise direction in the Figure) to push down the movable linearguide member 112, coupled to the movable framework 50 at the trendpivot.

Referring to FIG. 19 , there is shown a schematic perspective view of atilt mechanism 450 of the surgical table 2 in accordance with a furtherembodiment of the present invention. FIGS. 20 a and 20 b illustrate atilt frame 452 of the tilt mechanism 450 rotated about the tilt axis X-Xat two opposite end positions relative to a central level position.

As described above, the surgical table 2 has a trend mechanism forenabling at least a part of the tabletop 8 to be independently rotatedabout the trend axis T-T which extends in a transverse direction acrossthe tabletop 8. The trend mechanism enables at least a part of thetabletop 8 to be rotated about the trend axis T-T. The tilt mechanism450 is located between the tabletop 8 and the trend mechanism forenabling at least a part of the tabletop 8 to be independently rotatedabout the tilt axis X-X which extends in a longitudinal direction alongthe tabletop 8. The tilt frame 452 is located above the trend axis T-T.

The tilt axis X-X extends through the tilt frame 452 comprising a secondmovable framework. As described above, the trend and tilt mechanismcomprises the trend frame 50, which comprises a first movable frameworkmounted to at least one of the base 4 and the column 6. A first drivesystem, comprising the first and second actuators 54, 56, is fittedbetween the trend frame 50 and at least one of the base 4 and the column6 for rotating the trend frame 50 about the trend axis T-T.

The tilt frame 452, which comprises a second movable framework, ismounted between the trend frame 50 and the tabletop 8. The tilt axis X-Xextends through the trend frame 50 and the tilt frame 452. A pivotableconnection 453 is oriented along the tilt axis X-X and interconnects thetrend frame 50 and the tilt frame 452. Typically, the trend frame 50 islocated within the tilt frame 452.

The tilt axis X-X is above the trend axis T-T. The tilt frame 452 isabove the trend frame 50. The tilt frame 452 surrounds the trend frame50. The trend frame 50 and the tilt frame 452 are annular and the tiltframe 452 annularly surrounds the trend frame 50.

A second drive system 454 is fitted between the trend frame 50 and thetilt frame 452 for rotating the tilt frame 452 about the tilt axis X-X.The second drive system 454 is adapted to rotate the tilt frame 452about the tilt axis X-X over a tilt angle range of at least 50°, forexample by a tilt angle of at least +/−25° from a central levelposition. Typically, the second drive system 454 is fitted within thetilt frame 452 above the trend axis T-T.

Accordingly, the second drive system 454 is a drive arrangement to allowtable top tilt movement. The tilt frame movement is independent to andisolated from trend movement unlike some systems used on conventionaloperating tables where the tilt and trend drive actuators are bothconnected back to the column With the latter conventional arrangement,trend movement can instigate small amounts of tilt movement without thetilt drive being operated, which is not desirable.

With the structural arrangement of the preferred embodiments of thepresent invention, the tilt frame 452 is intentionally fitted outside ofthe trend frame 50 and rotates about the trend frame 50 and not thecolumn 6. This structural arrangement prevents skewing of the tabletop8, i.e. the tabletop being moved out of line with the longitudinal axisof the base 4) when both trend and tilt are applied, that wouldotherwise occur if the tilt frame was fitted inside the trend frame torotate about the column and with the trend frame rotating about the tiltframe.

In the embodiment illustrated in FIG. 19 , and FIGS. 20 a and 20 b , thesecond drive system 454 comprises a rack and pinion drive system 454.The rack and pinion drive system 454 comprises a curved rack 456 fittedto the trend frame 50, a rotatable pinion 458 fitted to the tilt frame452 and a drive motor 460 connected to the pinion 458 for rotating thepinion 458. In this embodiment, the pinion 458 is located above the rack456. The drive motor 460, with gearbox 461, is fitted to the tilt frame452.

The curved rack 456 typically has a diameter of at least 100 mm,optionally from 100 to 110 mm. Typically, an uppermost portion 462 ofthe curved rack 456 is no more than 105 mm above the tilt axis X-X,optionally from 95 to 105 mm above the tilt axis X-X.

The second drive system 454 preferably further comprises helical orsplit gears between the drive motor 460 and the pinion 458. In addition,the rack 456 and pinion 458 preferably have respective helical teethwhich mutually engage between the rack 456 and pinion 458.

These features are preferably provided to minimise backlash in the tiltmechanism 450, which therefore minimises movement or free play in thetabletop 8. The position of the pinion 458 relative to the rack 456 maybe adjustable so that a close mesh between the rack 456 and pinion 458can be reliably achieved.

Preferably, the tilt mechanism 450 also comprises a force applicator 414which can be switched between an operative mode in which a force isapplied to the rack and pinion drive system tilt mechanism 450 toenhance engagement between the rack 456 and pinion 458 and aninoperative mode in which the force is not applied or is reduced ascompared to the operative mode.

In an alternative embodiment illustrated in FIG. 21 , a rack and piniondrive system 504 comprises a curved rack 506 which is located above thepinion 508. The curved rack 506 fitted to the trend frame 50, therotatable pinion 508 is fitted to the tilt frame 502 and a drive motor510, fitted to the tilt frame 502, is connected to the pinion 508 forrotating the pinion 508.

Again, the curved rack 506 typically has a diameter of at least 100 mm,optionally from 105 to 115 mm. Typically, an uppermost portion of thecurved rack 506 is less than 105 mm above the tilt axis X-X, optionallyfrom 80 to 90 mm above the tilt axis X-X.

In the embodiments of FIGS. 19 to 21 , as shown in FIG. 19 , at leastone damper element 412 (schematically illustrated) may be fitted betweenthe trend frame 50 and the tilt frame 402 for damping the motion of thetilt frame 402 about the tilt axis X-X. The damper element 412 typicallycomprises a gas spring or a rotary damper. In addition, a braking system414 (schematically illustrated) may be fitted to the tilt frame 402 forbraking the motion of the tilt frame 402 about the tilt axis X-X.Typically, the braking system 414 comprises an electrical brake.

The embodiments of FIGS. 19 to 21 provide a drive arrangement to allowtable top tilt movement. The tilt frame 402, 502 movement is independentto, and isolated from, the trend frame 50 movement. In contrast, somesystems used on conventional surgical operating tables provide that thetilt and trend drive actuators are both connected back to the column;with such an arrangement, trend movement can instigate small amounts oftilt movement without the tilt drive being operated, which introducesclearly undesirable tilt movement.

The embodiments of FIGS. 19 to 21 also provide that the tilt frame 402,502 is fitted outside of the trend frame 50 and rotates about the trendframe 50 and not the column 6. This prevents the tabletop skewing (i.e.the tabletop being moved out of line with the longitudinal axis of thebase) when both trend and tilt are applied, that would otherwise occurif the tilt frame is fitted inside the trend frame and rotates about thecolumn with the trend frame rotating about the tilt frame.

The tilt drive mechanism includes a motor and gearbox drive unit with acurved rack and pinion arrangement to allow tilt movement of thetabletop over a tilt angle range. The tilt angle range is a minimum of25° in either direction from a level position, providing a minimum totaltilt angle movement of at least 50°. The large rack diameter enableshigh torque transmission loads to be achieved in combination with a lowoverall height for the combination of the trend and tilt mechanism andthe column, for example having a vertical distance of less than 105 mmfrom the top of the curved rack to the tilt pivot axis T-T. This smallvertical height of the tilt drive mechanism helps to achieve a lowminimum overall tabletop height, typically less than 510 mm from thefloor to top of table top, in conjunction with the trend mechanism andcolumn as described with reference to FIGS. 1 to 14 .

In a further embodiment, as illustrated in FIG. 22 , the tilt drivesystem 600 comprises a belt drive system 604. As shown in FIG. 22 , thebelt drive system 604 comprises an endless belt 606 fitted to the tiltframe 602 via a rotatable driven element 612 such as a pulley wheel. Arotatable drive element 608, such as a pulley wheel, is fitted to thetrend frame 50 and engages the belt 606. A drive motor 610 is connectedto the rotatable drive element 608 for rotating the drive element 608.As the drive motor 610 rotates the drive element 608 in one of twoopposite rotational directions, the endless belt 606 correspondinglyrotates the rotatable driven element 612 and rotates the tilt frame 602about a desired tilt angle in a desired tilt direction. Alternatively,the endless belt may be fitted to the trend frame 50 and the rotatabledrive element is fitted to the tilt frame 602.

A further embodiment of the present invention is illustrated in FIGS.23, 24 and 25 . According to this embodiment, as for the firstembodiment, a surgical table comprises a base for standing on a floor; acolumn mounted on and extending from the base; and a tabletop providinga patient support surface. As shown in FIGS. 23, 24 and 25 , a movableframework 700 is provided to which at least a part of the tabletop (notshown) is directly or indirectly fitted. A rack and pinion mechanism 702is fitted to the movable framework 700 between the tabletop and thecolumn for enabling the movable framework 700, and the part of thetabletop fitted thereto, to be rotated about a pivot axis 704.

In the illustrated embodiment, the pivot axis 704 is a tilt axisextending in a longitudinal direction along the tabletop, and themovable framework 700 is a tilt frame 700 pivotally fitted around atrend frame 50 as described above for the embodiment of FIGS. 2 to 17 b.

The rack and pinion mechanism 702 comprises a pair of opposed first andsecond curved racks 706, 708 mounted on opposite sides of the pivot axis704. The racks 706, 708 face inwardly towards the pivot axis 704 and areoriented upwardly. A pair of first and second rotatable pinions 710, 712is provided, and each first and second pinion 710, 712 arranged toengage a respective first and second curved rack 706, 708. Each curvedrack 706, 708 typically has a radius of at least 200 mm, optionally from200 to 230 mm. Each pinion 710, 712 typically has a radius of at least30 mm, optionally from 30 to 45 mm, for example about 38 mm.

In this embodiment, the movable framework 700 is a first movableframework, in particular a tilt frame pivotable about the tilt axis, andthe curved racks 706, 708 are fitted to a second movable framework, inparticular a trend frame pivotable about the trend axis, located beneaththe first movable framework 700.

A drive system 714, including a drive motor 716 and gearbox 717, isconnected to the pinions 710, 712 for rotating the first and secondpinions 710, 712 in a common rotational direction. In other words, asshown in the side views of FIGS. 23 and 24 , when the first pinion 710is rotated in a clockwise direction, the second pinion 712 is rotated ina clockwise direction, and vice versa. The drive system 714 isconfigured so that the first and second pinions 710, 712 move inopposite respective upward or downward directions along the respectivefirst and second curved racks 706, 708 to rotate the movable framework700 about the pivot axis 702.

The drive system 714 is fitted to the movable framework 700. The firstand second pinions 710, 712 are fitted to the movable framework 700. Thecurved racks 706, 708 are fitted to the trend frame. The drive system714 comprises a primary drive wheel 722 which is coupled, directly asillustrated or by additional gear wheels (not shown), to the first andsecond pinions 710, 712. The drive motor 716 is adapted to be driveablein opposite rotational directions to rotate the primary drive wheel 722in opposite rotational directions and thereby pivot the movableframework 700 in opposite rotational directions.

The movable framework 700 is configured to be pivotable about the pivotaxis 704 in opposite rotational directions about a central position ofthe movable framework, 700. In the central position, the first andsecond pinions 710, 712 each engage the respective first and secondcurved racks 706, 708, as shown in FIGS. 23 and 24 .

Furthermore, the first and second pinions each engage the respectivefirst and second curved racks 706, 708 over a preset angular range ofthe movable framework 700 about the central position. Typically, thepreset angular range extends to at least +/−5° about the centralposition, for example at least +/−7° about the central position.

Outside the preset angular range, as shown in FIG. 25 an upper pinion ofthe first and second pinions 710, 712 is above, and out of contact with,the respective first and second curved rack 706, 708 and the lowerpinion of the first and second pinions 710, 712 remains engaged with therespective first and second curved rack 706, 708.

Each curved rack 706, 708 has an upper free end 718, 720 and therespective first and second pinion 710, 712 is configured to be locatedabove the respective first and second curved rack 706, 708 outside thepreset angular range.

In an alternative embodiment, the movable framework 700 is configured tobe pivotable about the trend axis extending in a transverse directionacross the tabletop. The pivot axis 702 is the trend axis. The curvedracks 706, 708 are fitted to the column and are in a fixed positionrelative to the column.

The twin rack and pinion inclination mechanism of FIGS. 23, 24 and 25 ,whether used to incline a tilt frame about a tilt axis, with the tiltframe mounted on a trend frame, or whether used to incline a trend frameabout a trend axis, with the trend frame mounted on a column or a tiltframe, provides a number of advantages. In particular, by providing atwin rack and pinion inclination mechanism, at low inclination anglesboth pinions are engaged with a respective curved rack, so the load oneach rack/pinion is low, but the total load and torque applied by thepair of racks and pinions can be very high. Furthermore, the diameter ofeach curved rack can be high, and the diameter of the pinions can alsobe high, and so the number of teeth engaged between each rack andassociated pinion can also be high, thereby enhancing the contact areabetween the rack and pinions to allow high torque transmission. Thesehigh torques can be achieved at low angles of inclination of the movableframework, while keeping the height of the torque transmission systemlow.

When used for inclining a trend frame, the twin rack and pinioninclination mechanism of FIGS. 23, 24 and 25 can be fitted around acolumn, for example when the trend pivot is fitted to the column, andbelow the top of the column. This provides the advantage of a lowoverall tabletop height.

The preferred embodiments of the present invention can provide that theancillary actuator for controlling the height of the trend axis relativeto the column can be locked, either directly by a locking mechanismtherein or by using a separate braking mechanism. This minimisesundesirable lateral movement or free play in the tabletop.

It may therefore be seen that the preferred embodiments of the presentinvention can provide a highly versatile column and trend mechanismwhich can provide a wide range of trend angles and a wide range oftabletop heights in a compact unit having a small footprint. The columnhas a small footprint yet high loading capacity and high torsionalrigidity. The column has a small height yet a high stroke.

In the preferred embodiments of the present invention, leadscrewactuators are used in which the lifting load is entirely through theleadscrews. Accordingly, no rotary bearings are required to support theload on the tabletop.

In the preferred embodiments of the present invention, the trend frameactuators can be driven synchronously with column height adjustment.

In the preferred embodiments of the present invention, position sensorscan be integrated into the column sections.

The preferred embodiments of the present invention can provide a minimumtabletop height (excluding mattress thickness) of no greater than 510 mmfrom the floor surface.

The preferred embodiments of the present invention can provide a minimumcolumn height of less than 380 mm from the base of the surgical table.The trend pivot is below the top of the column and is less than 290 mmfrom the base of the surgical table. A low minimum tabletop height isachieved because component or assemblies above the column can be lowereddirectly onto the column without the need for clearance above thecolumn. In contrast, in a conventional surgical table design with fixedtrend pivot positions, clearance above the column is required to allowfor trend and tilt movement. By providing an adjustment of the positionof the trend pivot relative to the column height, the height adjustmentof the tabletop can be increased compared to the height adjustment ofonly the column, while still facilitating a low minimum tabletop height.

The contracted height to stroke ratio is maximised by usingthrough-spindle electric actuators, in which the screw can be driventhrough the gearbox, in the preferred embodiments of the invention. Thisin turn provides that a low table height and large trend angles can beachieved. The use of such actuators provides that the gearbox does notadd to the height of the actuator compared to conventional actuatorsthat have the screw connected directly above the gearbox.

The preferred embodiments of the present invention can also provide atabletop height adjustment range of up to 645 mm.

The preferred embodiments of the present invention can provide that theratio of the overall column and trend frame height extension to theminimum height of the column and trend frame is far higher than iscurrently achieved by any commercially available surgical table. Forexample, the surgical table of the present invention can provide thatthe ratio between the extended maximum height of the tabletop from thefloor and the retracted minimum height of the tabletop from the floor isat least 2.1, and typically greater than 2.25. These dimensions canprovide a trend pivot centre height, from the base of the surgicaltable, with a maximum/minimum ratio of at least 3.22 (calculated as[(290+645)/290]). Correspondingly, these dimensions can provide a trendpivot centre height, from the floor, with a maximum/minimum ratio of atleast 2.26 (calculated as [(510+645)/510]).

The preferred embodiments of the present invention can also provide acolumn height adjustment range of at least 525 mm.

The preferred embodiments of the present invention can also provide avertical lifting capacity of 550 kg and an offset loading momentcapacity of at least 1600 Nm.

The preferred embodiments of the present invention can provide large,steep trend angles of at least 45 degrees, typically up to 90° fromendpoints of +45° to −45°, at low column heights while still providingsufficient clearance for table coverings and ancillary components aroundthe column. The trend axis, and trend frame, can be raised above thecolumn to provide a high level of clearance from the column to permitlarge trend angles even at low tabletop heights.

The preferred embodiments of the present invention can provide twoactuators which support offset loads on the trend frame, which improvesthe dynamic lifting performance and offset loading capacity at a giventrend angle. Furthermore, more compact and less powerful actuators canbe employed to achieve a high dynamic performance.

The preferred embodiments of the present invention can provide astabiliser system which minimises lateral loading on the actuators forraising the trend frame and varying the trend angle, providing that theactuator loading is primarily in line with the axis of the elongateelement of the actuator. This reduces bucking loads on the actuators,particularly at high extension dimensions, for example up to 210 mm, forthe elongate element of the actuator. The stabiliser system can enablethe use of smaller diameter elongate elements of the actuators, withcorrespondingly smaller drive systems and gearboxes, permits a smallerfootprint, large tilt and trend angles and maximum patient imaging onopposite sides of the column. The stabiliser system can also minimisefree play or movement in the tabletop by minimising lateral movement inthe actuator system. Hard end stops may be integrated into thestabiliser system to securely limit the effective range of movement ofthe actuators. Position sensors can be integrated into the stabilisersystem, remote from the actuators and the associated drive systems.

Various modifications can be made to the above-described embodimentswithout departing from the scope of the present invention, which isdefined by the claims.

The invention claimed is:
 1. A surgical table comprising: a base forstanding on a floor; a column of adjustable height mounted on andextending from the base, wherein the column comprises a plurality ofcolumn elements which form a telescoping assembly, the plurality ofcolumn elements comprising an outer column element and an inner columnelement, with the outer column element externally surrounding the innercolumn element and defining an external surface of the column when thecolumn elements are telescoped into a contracted configuration; atabletop providing a patient support surface; a movable frameworkmounted between the tabletop and the column for enabling at least a partof the tabletop to be rotatable about a trend axis extending in atransverse direction across the tabletop; and an actuator mechanismcoupled between the movable framework and the column and arranged toraise and lower the movable framework and the trend axis relative to thecolumn and to rotate the movable framework about the trend axis, whereinthe actuator mechanism is fitted to an external surface of the outercolumn element and is adapted to move the movable framework between alowermost position, at which the trend axis is below the upper end ofthe column and extends through an upper part of the outer column elementwhich surrounds the inner column element when the column elements aretelescoped into the contracted configuration, and an uppermost position,at which the trend axis is spaced at spacing height from an uppermostpart of the column.
 2. A surgical table according to claim 1, wherein inthe lowermost position the movable framework is entirely below the upperend of the column.
 3. A surgical table according to claim 1, wherein inthe uppermost position the movable framework is above the upper end ofthe column.
 4. A surgical table according to claim 3, wherein in theuppermost position the movable framework is entirely above the upper endof the column.
 5. A surgical table according to claim 1, wherein theactuator mechanism is external of the column.
 6. A surgical tableaccording to claim 1, wherein the actuator mechanism comprises first andsecond actuators, the first actuator being connected to a first portionof the movable framework and the second actuator being connected to asecond portion of the movable framework, the first and second portionsbeing mutually spaced and located on opposite sides of the trend axis.7. A surgical table according to claim 6, wherein the first and secondportions are located on opposite sides of a central axis orthogonal tothe trend axis and extending through the movable framework.
 8. Asurgical table according to claim 6, wherein the movable framework issubstantially rectangular and the first and second portions are locatedat diagonally opposite corners of the movable framework.
 9. A surgicaltable according to claim 6, wherein the first and second actuators arethe only actuators coupled between the column and to the movableframework for causing movement of the movable framework relative to thecolumn.
 10. A surgical table according to claim 6, wherein a first endof each of the first and second actuators is pivotally coupled to themovable framework and a second end of each of the first and secondactuators is pivotally coupled to an external surface of the column. 11.A surgical table according to claim 6, wherein the first and secondactuators each comprise an electrical linear actuator.
 12. A surgicaltable according to claim 6, wherein the first and second actuators eachcomprise an elongate element having an upper end connected by a pivotjoint to the movable framework and a drive assembly coupled to a lowerportion of the elongate element for extending, or retracting, theelongate element so as respectively to raise, or lower, the respectivefirst and second portions of the movable framework.
 13. A surgical tableaccording to claim 12 wherein the elongate element comprises a leadscrewand the drive assembly is adapted to rotate the leadscrew to extend, orretract, the leadscrew so as respectively to raise, or lower, therespective first and second portions of the movable framework.
 14. Asurgical table according to claim 13 wherein the leadscrew extendsentirely through the drive assembly so that a lower end of the leadscrewis below the drive assembly at least when the leadscrew is retracted.15. A surgical table according to claim 12, wherein the elongate elementis linear and is inclined at an acute angle from a plane including alongitudinal axis of the column and the trend axis so that the upper endis oriented further from the plane than the lower portion.
 16. Asurgical table according to claim 15, wherein the elongate elements ofthe first and second actuators are oriented in opposite directions fromthe plane.
 17. A surgical table according to claim 15, wherein thesecond end of each of the first and second actuators is pivotallycoupled to the column and the acute angle of inclination of eachelongate element from the plane decreases as the extension of theelongate element increases.
 18. A surgical table according to claim 7,wherein the first and second actuators are each inclined at a respectiveacute angle in opposite directions from a plane including a longitudinalaxis of the column and the trend axis so that the upper first end ofeach of the first and second actuators is oriented further from theplane than the respective lower second end.
 19. A surgical tableaccording to claim 1, wherein the movable framework defines an internalopening which is larger than the upper end of the column and theactuator mechanism is capable of lowering the movable framework relativeto the column to the lowermost position in which the movable frameworkis below the upper end of the column and surrounds the column.
 20. Asurgical table according to claim 19, wherein in the lowermost positionthe movable framework is entirely below the upper end of the column. 21.A surgical table according to claim 1, wherein the actuator mechanism iscapable of raising the movable framework relative to the column to theuppermost position in which the movable framework is above the upper endof the column.
 22. A surgical table according to claim 21, wherein inthe uppermost position the movable framework is entirely above the upperend of the column.
 23. A surgical table according to claim 1, whereinthe actuator mechanism is external of the column.
 24. A surgical tableaccording to claim 1, further comprising: at least one linear guidemechanism extending along at least a portion of the length of thecolumn, the at least one linear guide mechanism comprising a first partcoupled to the column and a second part pivotally coupled to the movableframework at the trend axis, the first and second parts being relativelymovable along a linear axis of the at least one linear guide mechanismto enable the movable framework to be translated along the linear axisby relative movement of the first and second parts.
 25. A surgical tableaccording to claim 24 wherein there are a pair of opposite linear guidemechanisms, each pivotally coupled to the movable framework at arespective spaced location along the trend axis, and mounted to oppositesides of the column, and the surgical table further comprising a bracemechanism coupled to the opposite linear guide mechanisms.
 26. Asurgical table according to claim 25, wherein the linear guidemechanisms and the brace mechanism are external of the column.
 27. Asurgical table according to claim 25, wherein the brace mechanismcomprises a brace element having a central member and two opposite endmembers that are inclined to the central member and oriented in a commondirection, and each end member is rigidly affixed to a respective linearguide mechanism.
 28. A surgical table according to claim 27, wherein thetwo opposite end members are orthogonal to the central member.
 29. Asurgical table according to claim 25, further comprising at least onelinear brace guide between the brace mechanism and the column.
 30. Asurgical table according to claim 24, wherein the first part is a fixedlinear guide member, fixed to the column, and the second part is amovable linear guide member, coupled to the movable framework.
 31. Asurgical table according to claim 30, wherein the first part is anelongate channel and the second part is an elongate slider within thechannel.
 32. A surgical table according to claim 25, wherein the linearguide mechanisms are provided with a locking mechanism to lock thelinear guide mechanisms at a selected height, and thereby lock the trendaxis at a selected height and/or a braking mechanism to brake themovement of the linear guide mechanisms.
 33. A surgical table accordingto claim 1, further comprising a plurality of linear motion guide unitsbetween the or each pair of adjacent column elements, the linear motionguide units extending in a telescoping direction and being mutuallyspaced.
 34. A surgical table according to claim 33, wherein theplurality of linear motion guide units between the or each pair ofadjacent column elements comprises a pair of linear motion guide unitswhich are located on opposite sides of the trend axis and on oppositesides of a central axis orthogonal to the trend axis and extendingthrough the movable framework.
 35. A surgical table according to claim33, wherein the column has a substantially rectangular cross-section andthe pair of linear motion guide units are located at opposite corners ofthe rectangular cross-section, the plurality of column elements furthercomprises an intermediate column element between the outer columnelement and the inner column element, and wherein a first pair of linearmotion guide units between the outer column element and the intermediatecolumn element are located at first opposite corners of the rectangularcross-section and a second pair of linear motion guide units between theinner column element and the intermediate column element are located atsecond opposite corners of the rectangular cross-section.
 36. A surgicaltable according to claim 33, wherein each linear motion guide unitcomprises an elongate channel fixed to one column element of the pair ofadjacent column elements and an elongate bar fixed to the other columnelement of the pair of adjacent column elements, the elongate bar beingslidable in the elongate channel.
 37. A surgical table according toclaim 1, further comprising a column drive mechanism located within theinner column element of the plurality of column elements, wherein thecolumn drive mechanism comprises a column actuator which has an upperend coupled to a drive surface affixed to an outer column element of theplurality of column elements.
 38. A surgical table according to claim 1,wherein when the column elements are telescoped into an extendedconfiguration the actuator mechanism, the movable framework and thetabletop are raised relative to the base.
 39. A surgical table accordingto claim 38, wherein the actuator mechanism is pivotally fitted to theexternal surface of the outer column element.